Yahoo recently launched day parting, but gave advertisers the option to day part based on either the advertiser's time zone or the searcher's time zone. Google AdWords time zone setting is only based on your account's time zone, i.e. the advertiser's time zone. So if you have some one looking for your services and you want to target them based on their time zone and not yours, you are somewhat out of luck in Google AdWords.

I ran a poll asking if advertisers want Google to add this feature and the overwhelming majority of the responses said yes. 88% of advertisers want the feature, 6% said they don't want it and another 6% said they don't care.